Background: Malnutrition may be an important cofactor explaining poor outcome of childhood bacterial meningitis (BM) in developing countries. We examined its effect in Latin American children. Methods: The weight-for-age z score was determined for 482 children with BM aged 2 months to 5 years. Normal weight (z score from >-1 to <+1), underweight (z score <-1) and overweight (z score >+1) children were compared on admission, in-hospital and at discharge. Using uni-and multivariate analysis, we sought for associations between malnutrition and 3 different outcomes. Results: The mean z score was-0.41 ± 1.54, with a normal distribution. Overall, 260 (54%) patients were of normal weight, 151 (31%) underweight, and 71 (15%) overweight. Compared with others, underweight patients had on admission a lower Glasgow coma score (P = 0.0006) and cerebrospinal fluid glucose concentration (P = 0.03), and a slower capillary filling time (P = 0.02). Their death rate was higher (P = 0.0004) and they survi